sum_{k=floor[(n+5)/2] mod 5} C(n,k).

Terms

a(0) =0a(1) =0a(2) =0a(3) =0a(4) =1a(5) =2a(6) =7a(7) =14a(8) =36a(9) =72a(10) =165a(11) =330a(12) =715a(13) =1430a(14) =3004a(15) =6008a(16) =12393a(17) =24786a(18) =50559a(19) =101118a(20) =204820a(21) =409640a(22) =826045a(23) =1652090a(24) =3321891a(25) =6643782a(26) =13333932a(27) =26667864a(28) =53457121a(29) =106914242